Investigation of the Role of Exopolysaccharide in Burkholderia tuberum

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Investigation of the Role of Exopolysaccharide in Burkholderia tuberum
Salma Soltani, Loyola Marymount University
Dr. Michelle Lum, Loyola Marymount University
Nitrogen is one of the most critical macronutrients for plant growth and its fixation is important for converting di-nitrogen into ammonia, a form that is usable by plants. Rhizobia engage in a nodulating, symbiotic nitrogen-fixing association with leguminous plants. Nodules are special root structures that allow for bacterial fixation of atmospheric nitrogen. It was long thought that only rhizobia of the alpha-proteobacteria nodulate plants. However, recently members of the beta-proteobacteria were found to engage in a nodulating symbiosis. We are interested in determining whether exopolysaccharide, which is critical for the alpha-rhizobia symbiosis, is necessary for the beta-rhizobia association. We are doing this by investigating the symbiotic relationship between Burkholderia tuberum (a beta-rhizobium) and Phaseolus vulgaris (black bean). We are working on generating and characterizing deletion mutants in B. tuberum. Our goal is to determine if exoY, which is required in the alpha-rhizobia symbiosis, is important in the beta-rhizobia symbiosis. A deletion construct to make a B. tuberum exoY mutant was created. Primers were designed to amplify by PCR the region upstream and downstream of the exoY gene. These regions were fused and ligated into the pJET cloning vector. The region was then subcloned into the pK18mobsacB vector to generate the deletion construct to be used for mutagenesis. We are now in the process of using the construct to generate the exoY deletion mutant. Once the mutant is generated, a nodulation assay will be conducted to determine the role of exoY in the symbiosis.